add support for brief output for link and addresses

add support for brief output for link and addresses

This adds support for slightly less output than is normally provided by
'ip link show' and 'ip addr show'.  This is a bit better when you have a
host with lots of interfaces.  Sample output:

$ ip -br link show
lo               UNKNOWN        00:00:00:00:00:00 <LOOPBACK,UP,LOWER_UP>
p2p1             UP             08:00:27:ee:0b:3b <BROADCAST,MULTICAST,UP,LOWER_UP>
p7p1             UP             08:00:27:9d:62:9f <BROADCAST,MULTICAST,UP,LOWER_UP>
p8p1             DOWN           08:00:27:dc:d8:ca <NO-CARRIER,BROADCAST,MULTICAST,UP>
p9p1             UP             08:00:27:76:d9:75 <BROADCAST,MULTICAST,UP,LOWER_UP>
p7p1.100@p7p1    UP             08:00:27:9d:62:9f <BROADCAST,MULTICAST,UP,LOWER_UP>

$ ip -br -4 addr show
lo               UNKNOWN        127.0.0.1/8
p2p1             UP             192.168.56.2/24
p7p1             UP             70.0.0.1/24
p8p1             DOWN           80.0.0.1/24
p9p1             UP             10.0.5.15/24
p7p1.100@p7p1    UP             200.0.0.1/24

$ ip -br -6 addr show
lo               UNKNOWN        ::1/128
p2p1             UP             fe80::a00:27ff:feee:b3b/64
p7p1             UP             7000::1/8 fe80::a00:27ff:fe9d:629f/64
p8p1             DOWN           8000::1/8
p9p1             UP             fe80::a00:27ff:fe76:d975/64
p7p1.100@p7p1    UP             fe80::a00:27ff:fe9d:629f/64

$ ip -br addr show p7p1
p7p1             UP             70.0.0.1/24 7000::1/8 fe80::a00:27ff:fe9d:629f/64

v2: Now with color support!
v3: Better field width estimation (except netdev names to keep output at a
decent width) and whitespace fixup.

Signed-off-by: Andy Gospodarek <gospo@cumulusnetworks.com>